1. Field of the Invention
The present invention relates to a method of collecting oil from crude oil residue.
2. Description of the Prior Art
Generally, crude oil residue generates at the time when a crude oil tanker or a storage tank at an oil refining plant is cleaned, or when residual substances are removed from a general oil tank.
As is well known, crude oil is present in opening in lime stones or sand stones together with natural gases and is confined therein being covered by poreless rocks overlying the stones. Therefore, when an oil well is dug below the rocks, the oil is drawn up due to an internal pressure in the ground or pumped by a pumping system. The oil thus obtained is then transported through a pipe system to an oil refining plant where it is classified into several divisions according to the differences in boiling points by distillation. The classified oils are further divided and refined to be separated into petroleum ether (having boiling points ranging between 60.degree. and 120.degree. C., e.g. pentane and hexane), ligroin, light naphtha (having boiling points ranging between 60.degree. and 120.degree. C., e.g. hexane and heptane), gasoline (having boiling points ranging between 40.degree. and 205.degree. C.), kerosene (having boiling points ranging between 175.degree. C. and 325.degree. C.) and light oil (having a boiling point of higher than 273.degree. C.) and, finally, lubricating oil is collected by vacuum distillation. As regards the rest, although some is utilized for asphalt, a large portion thereof is burned or merely disposed as waste as it is which often leads to a cause of public pollutions. Such crude oil residue mostly comprises sand, mud and rust but it nevertheless contains useful oils in no small quantities and it has long been desired to develop an effective method of collecting these oils to thereby meet the present day situation in which petroleum resources are scanty.